GraphingCalculator 3.2;
Window 48 458 507 1114;
PaneDivider 0;
FontSizes 18 14 12;
Slider 0 1;
SliderSteps 100;
SliderControlValue 86;
SliderMoving 1;
SliderVariable s;
2D.BottomLeft -2.859375 -4.671875;
2D.Axes 0;
2D.GraphPaper 0;
Text "<size=14>Diamo evidenza visiva al fatto che la tangente di un'ellisse in un punto <I>P</I> biseca l'angolo formato dalle rette che congiungono <I>P</I> ai fuochi.";
Color 3;
Expr x^2/9+y^2/4=1;
Color 3;
Expr function(P,s)=vector(3*cos(2*pi*s),2*sin(2*pi*s)),F=vector(sqrt(5),0),G=-F;
Color 3;
Expr 2/3*[cos(2*pi*s)]*[x-(3*cos(2*pi*s))]+[sin(2*pi*s)]*[y-(2*sin(2*pi*s))]=0;
Color 6;
Expr 2/3*[cos(2*pi*s)]*[x-(3*cos(2*pi*s))]+[sin(2*pi*s)]*[y-(2*sin(2*pi*s))]>0;
Color 3;
Expr vector(x,y)=F+t*[function(P,s)-F];
Color 3;
Expr vector(x,y)=G+t*[function(P,s)-G];
Color 6;
Expr abs(vector(x,y)-function(P,s))>0.4;
Color 3;
Expr F;
Color 3;
Expr G;